Success! I have managed to reconstruct the message from the fragments! I will post it here, so don't look if you want to do it by yourself.

[spoiler]Night is falling. We do not have long. Only the Forbidden Power will save us now. I leave an unimaginable treasure to the worthy; Alas, I cannot do more. I dare not speak of the Rift. I will hide the four keys. I am Inshir. Goodbye.[/spoiler]

(warning: contains spoilers if you have not reached everything mentioned so far!)

[spoiler](12/20 13:22:28) Chat.log started...
(12/20 13:30:34) Alexander Rush: So, that's it. What do you think?
(12/20 13:30:45) Ariana Brown: Looks sort of sinister...
(12/20 13:31:00) Ariana Brown: Like this guy Inshir was in trouble when he wrote it...
(12/20 13:31:28) Alexander Rush: But the four keys are the important part.
(12/20 13:31:50) Ariana Brown: I don't know, I just can't shake the feeling that something's wrong.
(12/20 13:32:15) Ariana Brown: Like, what could the Rift possibly be?
(12/20 13:32:34) Ariana Brown: And Forbidden Power can't be good, can it?
(12/20 13:33:05) Alexander Rush: Well when you think about it, the whole Yeesha journey thing would be considered forbidden power by the D'ni.
(12/20 13:33:15) Alexander Rush: Maybe it's not so bad...
(12/20 13:33:47) Ariana Brown: Don't you think we should do some research before we keep looking though?
(12/20 13:34:16) Alexander Rush: Well we're sort of at a dead end anyway.
(12/20 13:34:38) Alexander Rush: We know there are four keys, but we don't know where to find them.
(12/20 13:34:59) Ariana Brown: Maybe those other messages we've found will tell us.
(12/20 13:35:30) Alexander Rush: You mean that code in the Great Zero, and the red circles?
(12/20 13:35:46) Ariana Brown: Right. They must be there for a reason.
(12/20 13:35:56) Alexander Rush: But we still have no idea what they mean.
(12/20 13:37:47) Ariana Brown: Maybe one of the volunteers will figure it out.
(12/20 13:38:18) Alexander Rush: Let's hope so. I'm stumped right now.
(12/20 13:38:56) Ariana Brown: So, you're supposed to be the D'ni history expert; have you seen any reference to Inshir?
(12/20 13:39:02) Alexander Rush: Nope.
(12/20 13:39:17) Alexander Rush: These artifacts are all we have.
(12/20 13:39:34) Ariana Brown: That means we're going to be famous!
(12/20 13:39:42) Alexander Rush: And don't forget rich!
(12/20 13:40:54) Ariana Brown: Not if we can't figure this out. Maybe the message has hidden clues too...
(12/20 13:41:59) Alexander Rush: I wouldn't count on that... seems sort of irrelevant, but you never know.
(12/20 13:43:40) Ariana Brown: Oh! I just remembered I need to finish that chemical test. Gotta go...
(12/20 13:44:08) Ariana Brown: Remember, be careful.
(12/20 13:44:32) Ariana Brown: Somehow this doesn't seem like just an ordinary treasure hunt anymore.
(12/20 13:44:35) ...Chat.log stopped.
[/spoiler]

[spoiler]I've looked at the string of letters, and I can't find any other meaningful combinations other than 'The lock is here'. And those numbers may be some sort of sequence for a combination lock, denoted by the red circles. Any thoughts?[/spoiler]